Inertia time delay mechanism



April 11, 1961 N. CZAJKOWSKI 2,978,984

INERTIA TIME DELAY MECHANISM Filed April 10, 1958 2 Sheets-Sheet 1 INVENTOR. N. CZAJKOWSKI United States of America as represented :by the Secretary of the Navy Filed Apr. 10, 1958, Ser. No. 727,744

4 Claims. (Cl. 10280)' (Granted under Title 35, US. Code (1952), see. 266) r The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

v This invention relates to an improved ordnance inertia time delay mechanism of the type rendered operable by centrifugal force.

It is an object of this invention to provide a time delay mechanism for arming or detonatingan explosive pro;-

, jectile which mechanism is incapable of premature initiation.

-It is another object of this invention to provide a timing mechanism which provides a narrow range of time delays.

Still another object of this invention is the provision of an inertia weight timing system for use in a projectile utilizing a variable inertia system.

These and many other objects of this invention will be more readily understood when the following detailed description is read in the light of the appended drawings wherein like numerals designate like parts throughout the various views and in which: 7

Fig. l is a longitudinal section of the portion of a fuze in illustrating one preferred embodiment of this inven: tion in its initial inactive position;

Fig. 2 is a view similar to Fig. 1 showing the apparatus of this invention with the inertia weights in their outermost position;

Fig. 3 is a longitudinal section of the apparatus of this invention showing the device in the final or armed position; n V v .7 Fig. 4 is a section taken along lines 44 of Fig. 1.

Referring now with greater particularity to Figs. 1-3, it is seen that the inertia timing mechanism comprises a casing or shell 10 composed of an upper half 11 and a loweror rearward half 12. A pair of complementary mating recesses are formed in each of the halves 11 and 12 to provide an interior cavity 13 within which is disposed a rotatable rod 14 lying along the axis of rotation of the projectile and has cross arm 16 fixed thereto. One end ofmember 14 is threaded at 17 in a direction opposite to the sense of spin imparted to the projectile by the rifling of the gun from which it is fired. This threaded portion 17 is of slightly larger diameter than the remainder of member 14 and is threaded into an appropriate recess 18 formed within the first half 11 of the casing. Apertured plate 15 is secured to the interior of the casing and serves as a bearing surface for the upper end of rod 14 to prevent jamming of threaded portion -17 in receptacle 18 in the event of slight eccentricity of spin of the projectile.

A pair of relatively heavy inertia weights 19 are slidably disposed on the cross arm 16 on opposite sides of the rtatable member 14 and are held in proximity to the rotatable member by any suitable releasable means such, for example, as shown for purposes of illustration as a pair of spring biased latches or dogs 21 slideably disposed in bores in the second half 12 of casing and to r l Ce project into cavity 13 to restrain inertia weights 19 in the position shown in Fig. 2. Formed in the base of the rearward half 12 of the casing is a bore 22 filled with a primer explosive 23 which is adapted to be initiated by any suitablefuzing arrangement (not shown). A

body portion 24 having an enlarged recess 26 formed.

therein is secured to the lower half 12 of the casing so that the recess 26 is below rotatable member 14 and the bore 22. Disposed within this recess 26 is an eccentric disc 27 having its center of gravity 28 displaced from its center of rotation 29, causing the disc to tend to rotate about is center of rotation as the projectile rotates during flight because of the turning moment produced by the eccentric center of gravity. A minor segment of the disc 27 is removed along line A-B so that as the disc rotates, it is stopped in a positive manner as point B reaches a stop pin 30 fixed in the recess26 of body 24. Disc 27 contains a bore 31 formed therein which is adapted to receive the lower end of rotatable member 14 when the timing mechanism is in the initial position whereby rod 14 prevents rotation of disc 27. r a

A second bore 32 is also formed in disc 27 and contains an explosive detonator 33 which is adapted to be ititiated by the explosion of the primer 23 only when the bore 32 is in alignment with the bore 22. An explosive lead 34 is disposed within a bore 35 in body 24 for detonation of the booster (not shown) and the main charge (not shown). This lead is always in alignment with the primer 23 in bore 22 but is normally shielded therefrom by the disc 27. When the disc is rotated so that point B abuts pin 30, bore 32 is brought into alignment with bores 22 and 35 thus completing the powder train.

in operation the timing mechanism functions in the following manner. Upon firing of the projectile the dogs 21 are driven rearwardly against the biasing force of the springs by the setback force, thereby releasing the weights 19 and allowing them to move radially outward to the ends of the cross arms 16 as the projectile rotates. It should be noted that an enlarged knob 36 is formed at each end of the cross member to prevent the weights from becoming wedged against the wall of the cavity 13. Immediately priorto movement of inertia weights 19 along cross arm 16, the timing mechanism as a whole rotates with the same rotational speed as the casing within which it is disposed, that is to say there is no relative rotational movement between the various parts .of the mechanism. However, when weights 19 reach their outermost position, their moment of inertia has been changed due to the fact that the radial distance from the center of rotation. is efiectively increased since the rotatable member 14 lies along the axis of the projectile. Accordingly, the angular Velocity of the weights 19 and shaft 14 must decrease since the angular momentum must remain constant according to the law of conservation of momentum. This decrease in angular velocity of rotatable member 14 results in a relative rotational movement between member 14 and casing 10 threading the rotatablev member 14 into the receptacle 18 formed in the upper half 11 of the casing. After a predetermined number of revolutions of member 14, it is withdrawn from the bore 31 in eccentric disc 27 permitting the disc to whip around the point 29 until the point B abuts pin 30 thereby aligning detonator 33 with the charges 34 and 23 so that the projectile is now in the armed position and will be fired upon initiation of primer 23. It should be apparent that the delay inherent in this mechanism may be selectively altered by changing the pitch of the threaded bore 18 or by initially threading the member 17 a distance within this bore.

Furthermore, it would be obvious to anyone skilled in this art upon reading and comprehending the foregoing tion has been described in but one preferred embodiment it is not to be construed as so limited but is susceptible of many alterations and modifications without departing from the scope thereof and is to be construed as limite only by the scope of the appended claims.

What is claimed as new and desired to be secured by.

the axis of spin of the projectile, a rotatable rod having a threaded portion disposed within said threaded bore and an unthreaded portion rotatably extending through said second bore, a third bore formed within said casing and laterally spaced from said second bore, a primer explosive substantially filling said last-named bore, an

- explosive lead adapted to detonate the projectile and disposed in alignment with said primer explosive, an eccentric arming disc disposed between said primer explosive and said explosive lead and having a bore therethrough containing an explosive detonator normally displaced laterally from said primer and said explosive lead, a recess formed in said disc adapted to initially receive the unthreaded portion of said rod to prevent rotation of said disc, a transverse member fixed to said rod intermediate its ends to define a cross arm on each side of said rod, an inertia weight slideably disposed on each of the cross arms, detent means disposed in said casing and restraining said inertia weights in proximate relation to said rod, said detent means adapted to release said inertia weights upon the firing of the projectile, whereby said inertia weights move along the cross arm portion away from said rod to change their moment of inertia" and produce relative rotational movement between said rod and said casing to thread said rod into said threaded bore in said casing withdrawing said rod from the recess in said disc thereby permitting said disc to rotate and align the explosive detonator with said primer explosive and said explosive lead to arm the projectile.

2. An inertia time delay mechanism for use in a spinning body comprising a shell having first and second end portions, said first end portion having a threaded aperture, an arming disc rotatable within the interior of said shell at said second end portion from an initialsafe position to an armed position and having an off-center aperture, said disc having its center of gravity displaced from its center of rotation sufiiciently to rotate the disc from said initial position to the armed position, a rod having a first end portion engaging the walls ofsaid off center aperture to lock said disc in said initial position and having a second threaded end portion engaging the threads of said threaded aperture, a cross arm located on a central portion of said rod, inertia means slideably carried on said arm, releasable means mounted on said shell adjacent to said rod for normally retaining said inertia means against said rod, and means to actuate said releasable means whereby the spin of said body causes said inertia means to develop sufficient centrifugal force to move away from said rod and slide along said arm when said releasable means isreleased thereby screwing said rod into said'threaded aperture sufficiently to disengage the rod from said disc and cause the disc to be unlocked for movement to said armed position.

3. An inertia time delay mechanism for use in a spin ning body comprising a shell having at least two separate inner cavities, a threaded bore in one end of said shell forming an aperture between a first of said cavities and the exterior of said shell, an interior bore aligned with said threaded bore joining said. first and a second of said cavities, a disc having an off-center aperture rotatably maintained in said second cavity for movement from an initial position to a final position, said disc having its center of gravity ofi-setfromits center of rotation sulficiently to cause said disc to rotate in response to centrifugal force, a rod normally extending from said 0&- center aperture through said interior bore, through said first cavity and into contact with said threaded bore, said rod beingthreaded at the end portion in contact with said threaded bore for locking said disc in the initial position, an arm located on the central portion of said rod and extending on opposite sides at a right angle thereto into said first cavity, a pair of inertia members slidably carried by said arm on opposite sides of said rod, releasable detents mounted within said shell adjacent opposite sides of said rod for normally maintaining said inertia members against said rod, and means to actuate said releasable detents, a pin mounted in said shell to limit movement of said disc from said initial position to said final position, whereby the spin of said body causes said inertia members to slideaway from said rod and along said arm when said releasable detents are released thereby screwing said rod into said threaded bore and unlocking said disc forrotation to said final-position.

4. The apparatus of claim} wherein each end portion of said arm carries a means to stop the outward movement of said inertia members when said inertia members reach the end portions of said arm.

References Cited in the file of this patent UNITED STATES PATENTS 

